A basic method for the design of an oscillator using an electromechanical resonator

This paper summarizes a step-by-step method for designing an oscillator using an electromechanical resonator. The procedure starts with characterization of the resonator using a Vector Network Analyzer (VNA). Characterization allows the estimation of the quality factor Q, insertion losses (IL) and the relative phase-shift across the device. This information is used with two purposes, to translate the mechanical information to the electrical domain and to model the device in SPICE-like programs. Once in that simulator the sustaining electronics are designed using feedback theory and looking to satisfy the Barkhausen´s criterion. The method suggests providing extra gain to overcome additional losses from interconnections, PCB tracks, etc. VLSI editor programs can be used to layout the electronics following matching rules to minimize possible errors. This paper uses a set of free tools for the complete design process. As a result of the described method, a 4MHz oscillator using a crystal resonator interfaced with 2P3M 0.5µm IC is simulated and tested using the proposed procedure.